In many patients, gastrointestinal feeding is the preferred route of nutrient delivery with either the stomach or the upper portion of the small intestine being the two areas of major importance. Proper positioning of the feeding end of an enteral feeding tube in the desired area of the gastrointestinal tract has always been a problem. Even after proper positioning of the feeding end of a feeding tube in either the stomach or the small intestine, it is possible that the feeding end of the tube may unknowingly migrate from the selected area whereupon the patient may be subject to a risky feeding situation. A common method of initially positioning and then monitoring the proper positioning of the feeding end of such a gastrointestinal feeding tube has been by the use of X-ray. To repeatedly verify proper placement in this manner is not only cumbersome and expensive, but it also subjects the patient to unnecessary X-ray exposure.
One attempt to improve this situation is disclosed in U.S. Pat. No. 4,381,011 to Somers, dated April 26, 1983, wherein the pH or acidity of certain portions of a gastrointestinal tract are monitored by a pH measuring device positioned on the end of a feeding tube. However, as the pH may vary as the feeding process proceeds and may also be affected by extraneous factors, the monitored results may be seriously deficient as to the desired accuracy thereof. X-rays, etc. would probably be necessary for back-up purposes.
Further as to Somers and applicants' disclosure herein, the basic functions of the gastrointestinal system, the primary organs being the esophagus, the stomach, and the small intestine, are to mechanically transport foodstuff, chemically break down complex food ingredients, and to absorb processed foodstuff into the blood. Each of the noted primary organs possesses a muscle coat which contracts and propels the foodstuff along the system (peristalsis). This muscle contraction is controlled by nerve tissue via the movement of calcium and other ions from inside the cell to outside the cell and vice versa. This effect begins at a specific anatomical region called a pacemaker and propagates through the muscle mass of that organ. A complete cycle consists of depolarization, hyperpolarization and repolarization of the cell wall. The ion concentrations undergo increases and decreases during the cycle with each of the foregoing organs being characterized by its own cyclic frequency. This ion movement causes a chemical interaction at the surface of applicants' feeding tube electrodes whereby electrical potentials are created, voltage being the unit of measure for the difference between the two sources of electrical potential, applicants' electrodes. Applicants' feeding tube electrodes therefore detect any cyclic change in electrical voltage at their location in a patient's gastrointestinal tract.
Somers, on the other hand, depends on the digestive activities in the stomach where foodstuff is chemically broken down by pepsin and hydrochloric acid. The acid is produced in the stomach which is, therefore, normally a zone of high acid concentration relative to the esophagus and the small intestine due to the esophageal and pyloric sphincters at the entrance to and exit from the stomach, respectively. Acidity is measured in pH units which is the concentration of the hydrogen ion. Thus, a pH electrode undergoes a reaction which is dependent on the concentration of hydrogen ions adjacent thereto, which reaction produces an electrical potential. However, in pH systems the second potential source needed to measure a voltage must be provided by a reference electrode. It is obvious, therefore, that the pH system of Somers is affected to a much greater degree by gastrointestinal contents than is applicants' myoelectrography system disclosed herein, which myoelectrography system thus provides much more accurate results.